The present invention relates to a positive displacement pump of the general type disclosed in U.S. Pat. No. 4,948,351 which issued to the inventor of the present invention. This type of pump is particularly suited for handling sewage and other liquids which contain large solids and/or grit and abrasive materials or highly viscous materials, such as commonly encountered in residential sewage systems, waste water treatment plants and some industrial plants. As disclosed in the above patent, the positive displacement pump includes a base formed by a horizontal cylindrical conduit having opposite ends connected to flapper-type check valves. A vertical pump cylinder or housing is connected to the conduit and receives a piston which is reciprocated by a connecting rod extending from a crank arm driven by a motor gear reducer unit mounted on the housing.
When using such a pump, it has been found desirable for the pump to provide for an extended period of service without maintenance and for minimizing the time required for servicing the pump when maintenance is required. It is also desirable for the pump to be designed and constructed to prevent jamming of the reciprocating movement of the piston and to provide for a straight flow through conduit and for operating the pump at a relatively slow speed in order to extend the operating life of the pump components. It is further desirable to minimize the cost of the pump components which must be replaced after an extended period of pump operation in order to minimize the cost of servicing.